Adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4), one of the enzymes involved in purine metabolism, generates inosine and ammonia by removing an amino group coupled to the sixth carbon of adenosine and is present ubiquitously in nature.
Purine is synthesized via two pathways: a de novo pathway from a micromolecule precursor and a salvage pathway from the purine.
The salvage pathway is a process which reuses a foreign substance such as a degrading product generated by destroying unstable RNA within a cell, a nucleic acid of dead cell and a degrading product of nucleotides, and has the advantage of preventing a loss in vital energy and precursors. While the de novo pathway is preserved in all species, the salvage pathway varies depending on the kind of species.
It has been known that animals, plants and microorganisms have a specific inhibitor for each enzyme reaction and these inhibitors are mostly macromolecule peptides, but an inhibitor for the adenosine deaminase is generally an adenosine analogue which is a micromolecule compound having 500 Da or less of a molecular weight. Further, it is known that an enzyme inhibitor isolated from a microbial metabolite is a micromolecular substance having an extremely low toxicity with a new structure. Some inhibitors are very similar in their structures. The pharmaceutical composition of the present invention substrates, while others are completely different from their substrates.
As shown in the biosynthesis of antibiotics, there are cases that a plasmid is involved in a characteristic part of the procedure for biosynthesizing an enzyme inhibitor.
There have been reports on several microorganism-originated inhibitors for adenosine deaminase, such as coformycin (3-(α-D-ribo-furanosyl)-6,7,8-trihydroimidazol(1,3)diazepin-8(R)-ol) produced by Streptomyces kaniharaensis SF-557; and cordycepsin and 2′-deoxy coformycin produced by Aspergillus nidulans Y-176-2.
Coformycin produced by Streptomyces which produces formycin(7-amino-3-(β-ribofuranosyl)pyrazolo(4,3-d)pyrimidine) is a specific inhibitor for the adenosine deaminase and its inhibition is in competition with a substrate. Further, coformycin, together with formycin, shows a synergistic effect in inhibiting a bacterial growth in most bacteria except for Xanthomonas oryzae, and effectively inhibits a proliferation of Yoshida rat sarcoma cells.
Further, it has been reported 9-α-D-mannopyranosyladenine(1), 9-β-D-xylopyranosyladenine(2), 9-α-D-arabinopyranosyladenine(3), 9-α-L-rhamnopyranosyladenine(4), 9-β-D-fucopyranosyl adenine(5), 9-β-L-fucopyranosyladenine(6) as adenosine deaminase inhibitors. All of them except for 9-α-D-mannopyranosyladenine(4) act as competitive inhibitors, and 9-α-L-rhamnopyranosyladenine is known to have the strongest inhibitory effect.
It has been known that cytotoxicity is developed in a cell inhibited by erythro-9-(2-hydroxy-3-nonyl)adenine), an inhibitor of an adenosine deaminase, when the cell is treated with adenosine and deoxyadenosine.
It has been also reported that injection of an adenosine analogue such as arabinosyladenine, codycepin or formycin as into an animal can increase an anti-cancer effect.
An enzyme inhibitor has been effectively used for analyzing human physiological functions and medically important pathological phenomena, and in particular, specific inhibitors have been known useful for biochemical analyses of biological functions or pathogens. Further, the enzyme inhibitors are powerful means in discovering various characteristics of enzymes such as active sites of enzymes, in vivo roles and physiological functions, and they can be also applicable as markers for diagnosing various diseases or as therapeutic agents.
The study on adenosine deaminase has been conducted since 1980s when an inhibitor of adenosine deaminase was known as an inhibitor of an immune system based on the discovery that the deficiency in adenosine deaminase, an essential factor involved in immune system, leads to the decrease in T-lymphocyte and B-lymphocyte thus resulting in an immunodeficiency.
Further, it has been found that the adenosine deaminase inhibitor increases the amount of ATP synthesis in petroleum-decomposing yeast using adenosine as a substrate, and thus its application to ATP synthesis has been proposed.
The studies about enzyme inhibitors have been actively carried out at numerous research institutions. As a result, new metabolic systems or enzyme systems have been discovered, thus clarifying the controlling relationships among biophysical functions.
Most of adenosine deaminase inhibitors reported till now have been grouped to a purine analogue family, which is produced by Actinomycetes, but they are very toxic to human cells when applied for medical treatments, and therefore, it has been on urgent need to develop a new drug applicable for clinical trials.
Further, there has been no report on adenosine deaminase inhibitors produced by bacterial strains.
The present inventors have isolated a new bacterial strain from a soil which produces an adenosine deaminase inhibitor compound and found that the inhibitor compound has antibacterial and anticancer activities.